Conventionally, there have been provided direct current (DC) power sockets which can intercommunicate between terminal devices and power line carrier communication networks supporting telecommunications standards with the PD.
There are Power over Ethernet (PoE) technology and Universal Serial Bus (USB) technology as a PD technology using data lines.
As the USB technologies, there are USB 2.0 Standard up to maximum supply power of 2.5 W, USB 3.0 Standard up to maximum supply power of 4.5 W, and Battery Charging Standard (BCS) Revision 1.2 up to maximum supply power of 7.5 W according to the PD level.
Moreover, a USB Power Delivery (USB-PD) Specification Revision 1.0 is compatible with existing cables and existing connectors, and coexists also with the USB 2.0 Standard, the USB 3.0 Standard, and the USB-BCS Revision 1.2. In such a specification, values of the charging current and voltage is selectable within a range of voltage 5V-12V-20V and a range of current 1.5 A-2 A-3 A-5 A, and the USB electric charging and power transmission can be achieved to be 10 W, 18 W, 36 W, 65 W, and the maximum of 100 W.
DC/DC converters have been used as a power source for achieving such a PD, and insulated DC/DC converters (e.g., flyback converters, forward converters) have been used for such a DC/DC converter, for example.